1. Field of Invention
The invention relates to a room temperature storage-stable oligonucleotide liquid formulation. More particularly, the invention relates to a stable formulation of a phosphorothioate oligonucleotide designed to bind to Hsp27 mRNA that also minimizes aggregate formation.
2. Description of Related Art
Hsp-27 antisense oligonucleotide (ASO) is designed to bind to Hsp27 mRNA to inhibit the production of human Hsp27 protein. U.S. Pat. No. 7,101,991 describes a variety of Hsp27 ASO.
Early animal study doses of OGX-427, or Hsp27 ASO Seq. Id. No. 1, formulated in a phosphate buffered saline (PBS), in an isotonic solution at the target pH of 7.4, showed good biological effect. However, at higher concentrations of the ASO, the OGX-427 formulations formed non-covalent aggregates after several days under both ambient and refrigerated conditions, and as a result were undesirable for clinical use. A PBS formulation solution had performed satisfactorily for a similar antisense product (see U.S. Pat. No. 6,900,187 relating to a clusterin ASO) and it had been expected that a similar formulation solution could be used for HSP27 ASO. However as explained above and shown below, a PBS solution of HSP27 ASO was not practical as a clinical formulation.
Liquid formulations for injectable administration of ASO drug products have customarily been refrigerated to assure adequate long-term stability. Lyophilization of an oligonucleotide formulation to powder (freeze-drying) with reconstitution just prior to use can be utilized to provide drug product delivery system with adequate stability profiles. However, there are significant commercial benefits to liquid formulations of oligonucleotides, particularly those that remain stable under ambient (room temperature) conditions.
U.S. Patent Publication 2003/0119768 discloses observations regarding a 15-mer antisense sequence targeting c-myc mRNA, namely AACGTTGAGG GGCAT (Seq. ID No. 2). This sequence, which includes four consecutive G residues, was observed to undergo aggregation to formed multimers with increased toxicity. The publication therefore disclosed disruption of the multimers prior to use. One approach disclosed is addition of a saccharide cryoprotectant such as mannitol, sucrose, glucose, trialose or lactose prior to lyophilization. This was found to reduce multimer formation upon reconstitution with water. No information was provided about the long-term solution stability and avoidance of aggregation, however.
An ASO subject to aggregation would be an unfavorable clinical candidate for a company's drug pipeline, regardless of the biological efficacy, and would not be further developed. However, the biological characteristics of Hsp27 ASO in vivo were so favorable that an effort to overcome the problem of aggregation and stability when stored in a liquid formulation for extended time periods was made.
Additionally, it should also be noted that ASO therapeutics remain expensive to manufacture, and that any reduction in their waste or cost of storage would be an added benefit and might make the difference between a commercializable and non-commercializable drug.